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Fuels: Canopy Fuel Characteristics

  1. Canopy Cover-Percentage or Class
  2. Stand (Canopy)-Height-ft or m
  3. Canopy Base Height-ft or m
  4. Canopy Bulk Density-kg/m3 or lb/ft3

Canopy Cover - Percentage or Class

The forest Canopy Cover (CC) describes the percent cover or cover class of the tree canopy in a stand. Specifically, CC describes the vertical projection of the tree canopy onto an imaginary horizontal surface representing the ground’s surface. Estimate of CC is used in adjustment of 20 feet winds to mid-flame, fuel moisture conditioning, and spotting distance models.

The scale illustrates representative CC percentages and ranges within each cover class.

Image
Canopy Cover classification. This graphic depicts from above views of canopy cover and its effect on wind sheltering/reduction.

For surface fuels sheltered by a forest canopy on flat terrain. (Scott 2007)

Canopy Cover Wind Sheltering
CC ≤ 5% Unsheltered
5% < CC ≤ 10% Partially Sheltered
10% < CC ≤ 15% Partially Sheltered
15% < CC ≤ 30% Fully Sheltered, Open
30% < CC ≤ 50% Fully Sheltered, Open
CC > 50% Fully Sheltered, Closed

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Stand (Canopy) Height-feet (ft) or meters (m)

The Stand or Canopy Height (SH) describes the average height of the top of the vegetated canopy. SH estimates are used in adjustment of 20 feet winds to mid-flame and in spotting distance models.

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Canopy Base Height-ft or m

The forest Canopy Base Height (CBH) describes the average height from the ground to a forest stand's canopy bottom. Specifically, it is the lowest height in a stand at which there is a sufficient amount of forest canopy fuel to propagate fire vertically into the canopy. Using this definition, ladder fuels such as lichen, dead branches, and small trees are incorporated. Estimate of CBH is used in the Crown Fire Initiation model.

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Describing a Forest Canopy. This graphic highlights the way to think about the primary descriptors for crown fire prediction. Crown Bulk Density describes the crown fuel load and distribution. Stand Height describes height of canopy tops. Crown Base height represents the difficulty for surfaces fires to ignite the canopy. And Foliar Moisture content suggest how readily the canopy will burn.

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Canopy Bulk Density-kg/m3 or lb/ft3

The forest Canopy Bulk Density (CBD) describes the density of available canopy fuel in a stand. It is defined as the mass of available canopy fuel per canopy volume unit. Typical units are either kg/m3 (LANDFIRE default) or lb/ft3 (BehavePlus default). CBD estimates are used to determine the threshold spread rate, or surface wind speed, used to determine the likelihood of active crown fire.

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Canopy Bulk Density is a difficult concept to apply to crown fire predictions. This image shows that CBD varies with height above ground.

The following graph, also displayed in the Crown Fire section under Crown Fire Initiation and Propagation, displays the threshold surface 20 feet wind speed or Crowning Index, necessary for producing active crown fire given a specific canopy bulk density.

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Crowning Index. Based on Rothermel crown fire spread model, canopy bulk density can be related to the windspeed required to sustain crown fire.

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NWCG Latest Announcements

NWCG Equipment Technology Committee Releases Safety Warning: 25-001 Non-specification fire shelters

Date: January 15, 2025
Contact: Equipment Technology Committee

The Equipment Technology Committee (ETC) has released Safety Warning: 25-001 Non-specification fire shelters. Non-specification fire shelters claiming to meet Forest Service (FS) fire shelter specification 5100-606 were first found in February of 2023. As of September 2024, non-specification shelters are again being advertised and sold on the open market.

This Safety Warning outlines details and recommended procedures to purchase FS specification shelters made with materials and components that meet performance criteria and toxicity testing requirements outlined in FS Specification 5100-606. 

For additional information on identifying non-specification shelters, please view ETC Safety Warning 23-01.

References:

ETC Safety Warning 25-001: Non-specification fire shelters

NWCG Equipment Technology Committee

ETC Safety Warning 23-01

Paul Gleason Lead by Example Awards

Date: January 14, 2025
Contact: Leadership Committee

The NWCG Leadership Committee has awarded the 2023 Paul Gleason “Lead By Example” awards to individuals in the categories of Initiative and Innovation, Mentoring and Teamwork, and Motivation and Vision, as well as a Lifetime Achievement Award.

Congratulations to the awardees:

  • Sam Bowen, Superintendent of the Mark Twain Veteran Crew with the U.S. Forest Service.
  • Greg Titus, Zone Fire Management Officer for the St. Marks National Wildlife Refuge with U.S. Fish and Wildlife Service.
  • Renae Crippen, Manager of the Blue Mountain Interagency Dispatch Center with the U.S. Forest Service.
  • Eric Carlson, Instructor with OMNA International.

References:

Paul Gleason Lead by Example Award

Wildland Fire Leadership Development Program

Interview with Paul Gleason

Updated NWCG Standards for Water Scooping Operations, PMS 518

Date: December 19, 2024
Contact: Water Scooper Operations Unit

The NWCG Standards for Water Scooping Operations, PMS 518 establishes the standards for dispatching, utilizing, and coordinating water scooping aircraft on interagency wildland fires. These standards should be used in conjunction with the NWCG Standards for Aerial Supervision (SAS), PMS 505, and any local, state, or geographic/regional water scooping plans.

References:

NWCG Standards for Water Scooping Operations, PMS 518

Updated NWCG Standards for Aerial Supervision, PMS 505

Date: December 19, 2024
Contact: Interagency Aerial Supervision Subcommittee

The Interagency Aerial Supervision Subcommittee has updated the NWCG Standards for Aerial Supervision, PMS 505. PMS 505 establishes standards for aerial supervision operations for national interagency wildland fire operations. 

References:

NWCG Standards for Aerial Supervision, PMS 505